Phase Transition Behaviors of Hydroxypropyl Methylcellulose Induced By Small Molecular Weak Acids

In this paper, phase change material hydroxypropyl methylcellulose (HPMC) was chosen to investigate the influence of small molecular weak acids on its phase transition temperature. The results showed that all of the chosen small molecular weak acids such as acrylic acid (AA), methacrylic acid (MAA), DL-lactic acid (LA), citric acid (CA) and acetic acid (AAc) can trigger the decrease of phase transition temperature of HPMC at different pH. With the increase of pH, AA, LA, CA and AAc can further lower the phase transition temperature, on the contrary, the phase transition temperature of HPMC increased with MAA. The change range of LCST was largest around pKa compared with other pH values because triggering effect changed gradually from hydrogen bonding effect to salt effect upon the increase of pH. Besides, phase transition temperature can also be reduced by the increase of acid concentration. This is attributed to smaller distance between molecules caused by higher concentration leading to stronger hydrogen bonding effect or salt effect. This paper provided a new perspective to modulate the LCST of phase change material by small molecular weak acids at different pH.

A simple theoretical, quantitative approach to help understand the titration of weak acids and bases

What happens at the very beginning of the titration of a weak acid or base is a question sometimes asked by undergraduate students when introduced to the concept of buffer solution. To attempt to answer this question, a simple quantitative approach is developed, which also allows explaining more general properties of the weak acid or weak base titration process, while serving as well as an introduction to the theoretical, quantitative treatment of this subject. Using this approach, it can be shown that, at the beginning of the titration, the reaction between a weak acid (base) and a strong base (acid) does not occur on a one to one ratio when very small amounts of the strong base (acid) are added.

Quaternary Alloy Quantum Dots as Fluorescence Probes for Total Acidity Detection of Paper-Based Relics

Traditionally, the acidity of paper-based relics was determined by an extraction method and using a pH meter. This method could not obtain the total acidity of the paper-based relics because it only detected the concentration of free protons in the aqueous soaking solution. To overcome this defect, a new method for determining the total acidity of paper-based relics has been established by using quaternary alloy quantum dots. The quantum dots, CdZnSeS, modified by p-Aminothiophenol (pATP) were prepared, and their composition and structure were characterized. The fluorescence behavior of prepared quantum dots with acidity was investigated. The following results were obtained. The fluorescence of CdZnSeS-pATP quantum dots could decrease with increases in acidity because pATP dissociated from the surfaces of the quantum dots due to protons or undissociated weak acids. Based on this feature, a method for determining the acidity of paper-based relics was constructed, and this method was used to evaluate the acidity of actual paper-based relics. Obviously, for a given paper sample, since both free protons and bound protons can be determined by this method, the acidity measured by this method is more reasonable than that by pH meter.

Combining weak acids and fasting could be a viable strategy against infections by Ebola-like viruses

Ebola-like viruses could depend on chloride or HCl to deliver lethal assault on human cells, causing hemorrhaging, bleeding, diarrhea, etc. It may harbor stressful peptides which can be generated in vivo after infections. Fasting with boiled rice water or with orange juice for a few days can halt virion production. However, infection-triggered cell lysis can produce nutrients for viral proliferation. The adoption of highly diluted weak organic acids such as acetic acid or lactic acid for smearing skin or foot bathing can neutralize chloride or HCl after absorption, and raise cellular pH to minimize cell lysis. Integration of fasting/fruit juice intake and highly diluted weak acids might reduce mortality rates of Ebola-like virus infections. The intake of NaCl should be minimized as it can give rise to chloride or HCl in cell microenvironment. Many food ingredients such as vinegar and sauce contain salt. Clinical trials must be conducted before the regimen is available for use.

In(compatibility) of intravenous drugs in critical units: adult cohort

ABSTRACT Objectives: To analyze potential (in)compatibilities of intravenous drugs based on the scheduling prepared by the nursing team. Methods: historic cohort (retrospective) with 110 adults in critical units. Intravenous medications were identified concomitantly, whose pairs were analyzed for (in) compatibility using the screening system Trissel’s™ 2 Compatibility IV-Micromedex 2.0. Parametric and non-parametric statistic were used according to the nature of the variable. Results: 565 pairs of drugs were identified. Of these, 44.9% were compatible; and 8.8%, potentially incompatible. Most potentially incompatible pairs involved substances with alkaline pH such as phenytoin (32%) and sodium bicarbonate (8%) and weak acids such as midazolam (12%) and dobutamine (6%), which could result in precipitate formation. Conclusions: almost half of the mixtures simultaneously administrated was compatible, which indirectly reflects in the organized work between the nursing team and the clinical pharmaceutic in the discussions and decisions related to time scheduling.

Humic acids trigger the weak acids stress response in maize seedlings

Background Plants primed by humic acids showed physiological and molecular response against different abiotic stresses without the presence of stressor agents (salinity, drought, heavy metal toxicity). It is plausible that humic acids themselves can act as chemical priming substances in plants. We hypothesized that humic acids can trigger the weak acids stress response in cell plants acidifying the cytosol and thus eliciting the transduction signalling response cascade. Methods The dose–response curves of maize seedlings roots with different concentrations of humic, acetic and salicylic acids determined the most active and inhibitory concentration. These data were further used to evaluate changes on intracellular pH using BCECF-AM probe (2,7-bis(2-carboxyethyl)-5(and 6)-carboxyfluorescein, acetoxymethyl ester) and differential transcription level of genes related to weak stress response in plants by qPCR real time. Results Humic acids like short chain organic acids decrease the intracellular pH showed by the increased fluorescence of BCECF probe. The drop in cytosolic pH promoted by humic acids was not transient. We observed a high level of protein kinases related to cell energy-sensing and transcription factors associated to transduction of stress signalling. Conclusion The humic acids can be considered as a chemical priming agent, since in the appropriate concentration they can induce the typical plant abiotic stress response of weak acids inducing plant acclimation and enhancing the abiotic stress tolerance.